Labour leader David Shearer must be wishing he had never mentioned a recording of a remark the Prime Minister is said to have made to staff of the Government Communications Security Bureau in February about the Dotcom investigation. If any recording was made of John Key's visit to the agency that day, Mr Shearer does not have a copy of it, nor it seems does anybody else.

In a sense, it does not matter, Mr Key freely concedes he might have made the remark but cannot recall it. He says the Dotcom case was not on his mind in February. Today, he needs to assure Parliament he did not mislead it when he said he did not know until September that the GCSB had gone outside its brief to monitor Dotcom, who has New Zealand residency. But in the absence of a recording he will be able to turn defence into an attack on the Opposition Leader's credibility.

If the public finds the exchange tiresome it is because it sees clearly what has happened: the Prime Minister has not paid enough attention to the Dotcom case and the Opposition Leader is not a natural muck-raker.

Mr Shearer's deficiency, if it can be called that, presents him with the greater problem.

Labour needs him to make a public impact. He has tried the high road, getting out around the country to talk about real issues, but that made little impression on the polls. Now he is resorting to parliamentary point-scoring, which seldom moves the public but can lift his MPs' morale if done well.

They cannot be impressed by his miscue on the GCSB. But even if his tactics had been more adroit, it is doubtful that the issue would have given him a lift in the polls. Mr Shearer does not seem at ease in this sort of politics. It appears to be an effort for him to take an interest in the intricacies of the Dotcom saga and attack it with conviction.

He would be well advised to leave this sort of work to others in his team who are more naturally tenacious than he is. Leaders have to be true to themselves to command the respect of others.

Mr Shearer looked best last week at centre stage in an economic policy "summit" with fellow Opposition party leaders flanking him. Unfortunately for him, that effort was overwhelmed by the missing GCSB recording. If he has to fight on this level, he will not win.